The wireless local-area network (WLAN) technology known as “Wi-Fi” has been standardised by IEEE in the 802.11 series of specifications (i.e., as “IEEE Standard for Information technology—Telecommunications and information exchange between systems. Local and metropolitan area networks—Specific requirements. Part 11: Wireless LAN Medium Access Control ( MAC) and Physical Layer ( PHY) Specifications”). As currently specified, Wi-Fi systems are primarily operated in the 2.4 GHz and 5 GHz bands. The terms “Wi-Fi” and “WLAN” are used interchangeably throughout this application.
The IEEE 802.11 specifications regulate the functions and operations of the Wi-Fi access points or wireless terminals, collectively known as “stations” or “STA,” in the IEEE 802.11, including the physical layer protocols, Medium Access Control (MAC) layer protocols, and other aspects needed to secure compatibility and inter-operability between access points and portable terminals. Because Wi-Fi is generally operated in unlicensed bands, communication over Wi-Fi may be subject to interference sources from any number of both known and unknown devices. Wi-Fi is commonly used as wireless extensions to fixed broadband access, e.g., in domestic environments and in so-called hotspots, like airports, train stations and restaurants.
Recently, Wi-Fi has been subject to increased interest from cellular network operators, who are studying the possibility of using Wi-Fi for purposes beyond its conventional role as an extension to fixed broadband access. These operators are responding to the ever-increasing market demands for wireless bandwidth, and are interested in using Wi-Fi technology as an extension of, or alternative to, cellular radio access network technologies. Cellular operators that are currently serving mobile users with, for example, any of the technologies standardised by the 3rd-Generation Partnership Project (3GPP), including the radio-access technologies known as Long-Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS)/Wideband Code-Division Multiple Access (WCDMA), High Speed Packet Access (HSPA) and Global System for Mobile Communications (GSM), see Wi-Fi as a wireless technology that can provide good additional support for users in their regular cellular networks.
As used herein, the term “operator-controlled Wi-Fi” indicates a Wi-Fi deployment that on some level is integrated with a cellular network operator's existing network, where the operator's radio access network(s) and one or more Wi-Fi wireless access points may even be connected to the same core network (CN) and provide the same or overlapping services. The term “Wi-Fi offload” is commonly used in the efforts to standardise the integration of Wi-Fi to the cellular network and indicates that cellular network operators seek means to offload traffic from their cellular networks to Wi-Fi, e.g., during peak-traffic-hours and in situations when the cellular network needs to be off-loaded for one reason or another, e.g., to provide a requested quality-of-service, to maximize bandwidth, or simply for improved coverage.
Many of today's portable terminal devices (also referred to herein as “user equipments” or “UEs” or mobile devices or communication devices) support Wi-Fi in addition to one or several 3GPP cellular technologies. In many cases, however, these terminal devices essentially behave as two separate devices from a radio access perspective.
3GPP is currently working on specifying a feature or mechanism for WLAN/3GPP radio interworking which improves the control over how a terminal device (UE) steers traffic (e.g. data sessions, voice calls, etc.) between 3GPP radio access networks, RANs (i.e. cellular radio access networks operating according to a 3GPP-specified radio access technology) and WLANs belonging to the operator or its partners.
In this and related mechanisms, the RAN (e.g. the 3GPP-specified RAN or the WLAN RAN) should provide parameters to the terminal device which are used to perform ‘access selection’ (or ‘access network selection’) to decide which network (e.g. the 3GPP network or WLAN) the terminal device should connect to. When access selection has been completed there may be ‘traffic steering’ in which it is decided which traffic (e.g. which data sessions, etc.) should be routed over the 3GPP network and which should be routed over the WLAN.
3GPP has identified a few example parameters that could be used in this mechanism which include thresholds, traffic steering information and WLAN identifiers (e.g. service set identifiers, SSIDs).
The thresholds could be, for example, metrics such as LTE reference signal received power (RSRP), WLAN received channel power indicator (RCPI), etc, and a terminal device could be configured to connect to a WLAN if the LTE RSRP is below the signalled RSRP threshold at the same time that the WLAN RCPI is above the signalled RCPI threshold. 3GPP has also discussed that similar thresholds can be provided for steering traffic back from WLAN to a 3GPP network.
For the traffic steering part of the mechanism, it has been discussed that the 3GPP RAN (or some other part of the 3GPP network, such as a network node like a mobility management entity, MME) should indicate traffic steering information to the terminal device which could comprise, for example, the marking of particular bearers as to whether they should be offloaded to WLAN or kept in the 3GPP network.
The WLAN identifiers are provided in order to indicate to the terminal device which WLANs the terminal device can consider connecting to (e.g. WLANs operated by the 3GPP network operator).
The steering described above is intended to be used alone or in combination with an Access Network Discovery and Selection Function, when that function is deployed.
Access Network Discovery and Selection Function—The Access Network Discovery and Selection Function (ANDSF) is an entity defined by 3GPP for providing access discovery information as well as mobility and routing policies to the UE. ANDSF was an entity added to the 3GPP architecture in Release 8 of 3GPP TS 23.402 (See “Architecture Enhancements for non-3GPP Accesses,” 3GPP TS 23.402, v. 11.4.0 (Sep. 2012), available at www.3gpp.org). A simplified ANDSF architecture is depicted in FIG. 1. As shown in the figure, an ANDSF server 10 is provided that is added to a 3GPP network that comprises one or more base stations 12 (known as eNBs in LTE networks) and a gateway (GW) 14. The ANDSF server 10 is connected to a terminal device 16, and its main goal is to provide the terminal device 16 with access network information in a resource efficient and secure manner. The communication between the terminal device 16 and the ANDSF server 10 is defined as an IP-based S14-interface 18.
By supplying information about both available 3GPP and non-3GPP access networks (e.g. WLANs) to the terminal device 16, the ANDSF server 10 enables an energy-efficient mechanism of network discovery, where the terminal device 16 can avoid continuous and energy-consuming background scanning. Furthermore, the ANDSF provides the mobile network operators with a tool for the implementation of flexible and efficient terminal device steering of access mechanisms, where policy control can guide terminal devices 16 to select one particular radio access network (RAN) over another.